Feature: Configuration page for WAN-port

[Akira25]

On Devices with DSL-Modem, the WAN-Port gets configured automatically on the DSL-Port. In #92 we agreed on, that this is a good standard way.

For increased Usability, there should be a LuCI-Page similar to the Update-Wireless-Mesh-Page, which allows to configure the WAN-port easily via options.

Some main options should be:

• WAN on Modem
• WAN on LAN[x]-port

In that way, we keep compability with upstream OpenWrt.

[Noki]

I think it would be good to extended this to "Configure Ethernet Ports" because there are at least 3 commen scenarios to configure LAN ports:

• WAN on LAN[x]-port
• Mesh on LAN[x]-port
• normal LAN on LAN[x]-port

The interface could look similar to the interface on the switch configuration page:

[Akira25]

This issue was solved partly by #235 . Lets keep this as reference for the project new-freifunk-wizard.